1. Field of the Invention
This invention relates to a magnetooptical recording medium with which writing, reading, and erasing of information are performed through application of a laser beam.
2. Description of the Prior Art
In recent years, a substantial amount of effort has been directed toward the development of an optical recording medium which satisfies various requirements including high density, large capacity and high speed access.
Of a wide range of optical recording media, magnetooptical recording medium is most attractive due to its unique advantage that information can be erased after use and new information can be written thereon (see U.S. Pat. No. 3,965,463). The magnetooptical recording medium comprises a glass or plastic disk substrate and a perpendicular magnetization layer as a recording material which is formed on the substrate.
In general the recording medium has a concentric circular or spiral recording track, the direction of magnetization of which track is entirely forced to be for example downward (or upward) by a strong external magnetic field before writing an information. An information can be written with a presence and/or length of pit having a reversed, for example upward (or downward), magnetization against the primary direction of magnetization.